Antifreeze proteins (AFPs) have been identified in a number of organisms, such as fish, plants, and insects, to allow them to survive at subfreezing temperatures. They are all characterized by their ability to depress the freezing point of the solution without appreciably altering the melting point thereby producing a thermal hysteresis. Insect AFPs are often the most active AFPs (10-100 times more active than type I fish AFPs). The antifreeze activities of many AFPs can be further enhanced in the presence of certain co-solutes (called enhancers). Both low molecular mass chemicals and macromolecules have been identified as enhancers for AFPs and some of the enhancers do play a role in enhancing the antifreeze activity of AFPs physiologically. Some of the enhancers have been reported to bind AFPs specifically. The mechanism of the enhancement effect, however, is still poorly described. The AFP from the beetle Dendroides canadensis (DAFP) and the enhancers have been extensively studied. The binding of enhancers to AFP has been demonstrated as one important mechanism for the enhancement effect of enhancers on the antifreeze activity of AFPs. Is there a common mechanism for the enhancement phenomena in different AFP systems? In this project, we will examine an important beetle AFP system, a mealworm AFP from Tenebrio molitor (TmAFP) and the enhancers. We propose that the enhancement efficiency of the enhancers for TmAFP antifreeze activity depends on the physiochemical properties of the enhancers. We will assess the enhancement efficiency of selected amine derivatives on TmAFP antifreeze activity and correlate their enhancement efficiency with their differing physicochemical properties. We will identify the possible interactions between TmAFP and the enhancers and determine the key amino acids in TmAFP involving in binding to the enhancers. The study of AFPs and enhancers is essential to advance our understanding of the biological system and facilitate the development of highly efficient AFP systems for their practical biomedical applications, such as in preservation of tissues at low temperatures in the lab and in human health as well as other industrial applications, such as in frozen foods and in hydrate inhibition. The proposed research will provide insights into the molecular mechanism of AFP and AFP enhancers and resolve conflicting reports regarding the mechanism of action of AFPs. PUBLIC HEALTH RELEVANCE: The proposed work examines the role of enhancers on the antifreeze properties of antifreeze proteins (AFPs). Antifreeze protection is important in public health (e.g., preservation of tissues at low temperatures and food preservation). The results of the project will advance our understanding of how AFPs and enhancer work, and improve public health by facilitating the biomedical applications of AFPs and enhancers.